Lifting slings are commonly used to lift heavy loads, secure cargo, and for numerous other lifting and securing activities. During normal operation the lifting sling can be subjected to forces that can result in damage to the lifting sling materials. Such forces can include crushing, pinching, binding, and stretching to name a few. Damage to the lifting sling materials can cause catastrophic failure during use and as such is a critical concern to those who manufacture, sell, and use lifting slings.
A regular inspection of the lifting sling is typically required as an attempt to avoid catastrophic failure of the lifting sling under load. However, inspection of the lifting sling can be difficult in that much of the lifting sling may be covered or inaccessible. In addition, it can be very difficult to visually identify lifting sling over-stretching and other types of forces, traumas, or crushing types of lifting sling damage.
In addition to the inability to accurately determine by visual inspection lifting sling damage and in particular lifting sling damage to the core materials, damage by ultraviolet light can also render a lifting sling unsuitable for use. In this regard, and for example, nylon and polyester lifting sling materials can be damaged by excessive or prolonged exposure to ultraviolet light. As such, while visually appearing as though the lifting sling is suitable for use, the lifting sling can be prematurely rendered unsuitable for use by ultraviolet light that has damaged the nylon and polyester materials. It is only during loading conditions that a lifting sling having ultraviolet light damage may rupture causing a catastrophic failure.
In addition to lifting slings being damaged by excessive forces, crushing, pinching, binding, stretching, and ultraviolet light exposure, dirt and other contaminants can also cause damage to the lifting sling core materials. In this regard, dirt and contaminants can increase the abrasion among the lifting slings core materials and or core fibers. As such, the increased abrasion among the core materials can cause premature degradation of the lifting sling, and or result in a catastrophic failure of the lifting sling during use. Dirt and contaminants introduced into the core materials, causing an increase in abrasion of the core materials, are particularly damaging to nylon types and polyester types of lifting slings.
Currently users of lifting slings are encouraged to clean the lifting slings periodically to minimize the presence of dirt and contaminants within the lifting sling core materials. Though a good recommendation, in practice lifting slings find applications in factories, on truck beds, on loading docks, and other places where dirt and contaminants are plentiful and the washing of lifting slings on a regular basis is impractical.
In general, contaminants such as dirt, chemicals, ultraviolet light, and other elements that come in contact with the lifting sling can prematurely degrade the lifting sling and or cause catastrophic lifting sling failure. In addition, excessive heat exposure can cause the lifting sling to warp, melt, pit, or otherwise become damaged. As such, exposure to excessive heat can result in premature and permanent degradation of the lifting sling materials and lead to an increased possibility of catastrophic lifting sling failure under load.
Overstretching a lifting sling can also permanently damage the lifting sling and rendered it unsuitable for use. In this regard, applying a load to a lifting sling beyond the lifting slings rated safe limits can cause the lifting sling to stretch. Stresses resulting in overstretching of a lifting sling are particularly common and can permanently damage nylon and polyester types of lifting sling materials. Once over stretched the lifting sling cannot be repaired. In addition, once over stretched the lifting sling can no longer carry the maximum load for which the lifting sling is rated.
In an attempt to protect the lifting sling core materials and to extend the operational or service life of the lifting sling it is common to employ the use of a lifting sling cover or sheath. The cover or sheath is typically placed around the lifting sling core materials to provide an interface between the lifted or secured load and the lifting sling core materials. In this regard, the cover provides protection to the lifting sling core against abrasions, cuts, crushing, binding, and other similar load related forces and injuries.
Lifting sling covers or sheaths can however prevent a thorough inspection of the lifting sling since the cover or sheath is typically wrapped around the lifting sling core materials keeping at least a portion of the lifting sling core materials hidden from sight. The problem of lifting sling safety and the use of covers and sheaths is further complicated in that, with a cover or sheath wrapped around the lifting sling core materials, cleaning dirt and contaminants from the lifting sling core materials is more difficult.
In addition to keeping dirt, chemicals, and other contaminants trapped and concealed within the lifting sling core materials, the lifting sling cover or sheath can require an extensive manufacturing process to fabricate. In this regard, covers or sheaths can require extensive stitching or other fabricating steps to secure the shape and fit of the cover or sheath around the lifting sling core materials.
Furthermore, lifting sling covers and sheaths are designed to cover the lifting sling core materials in a loose fitting fashion. This loose fitting fashion tends to cause the covers or sheaths to slide back and forth over the lifting sling core materials. The ability of the covers or sheaths to slide back-and-forth over the lifting sling core materials can result in the lifting sling's inability to grip the load and otherwise promote slippage of the load. Shifting loads can be an extreme danger and as such a lifting sling that has an inability to reliably grip the load and otherwise minimize slippage of the load is of little value and is a safety risk.
Concerns of safety, damage, and catastrophic failure of the lifting sling has given rise to numerous safety recommendations in the industry. Such safety recommendations include employing regular inspections of the lifting slings, as well as promoting other safeguards such as cleaning the lifting slings regularly. Safety, damage, and catastrophic failure of lifting slings has also given rise to attempts to protect the lifting sling from excessive abrasion, and other crushing, or pinching forces, as well as other types of traumas by utilizing covers or sheaths.
Attempts in the lifting sling industry to better manage the operational capabilities and suitability for use of the lifting sling has seen the use of optical inspection methods aimed at determining the suitability for use of the lifting sling. Such methods have seen the use of fiber optic cables that require a flashlight or light source and a skilled individual to evaluate test results as one way of determining the suitability for use of a lifting sling.
In this regard, a skilled individual performing a test can direct a flashlight beam or other light source into one end of a fiber optic cable and visually determined if the light source is present at the other end of the fiber-optic cable. Subjective and clumsy, this test then assumes that if forces applied to the lifting sling have not damaged the fiber optic cable, then the lifting sling is suitable for use.
In actuality there is little correlation between damage to a fiber-optic cable located in proximity to lifting sling core materials and damage to the lifting sling core materials themselves. Furthermore, fiber optic cable tests do not take into consideration dirt, chemicals, heat, ultraviolet light, and other destructive conditions as well as excessive loading and stretching of the lifting sling core materials, all of which can degrade the lifting sling and or cause catastrophic failure under load of the lifting sling.
In addition, the use of a cover or sheath can reduce the effectiveness of fiber optic cable inspection methods and the use of a cover or sheath may prevent the fiber optic cable from being subjected to the same forces as the lifting sling core materials.
There is a long felt need for a lifting sling that can overcome the limitations of the current lifting slings available on the market today. Such limitations can include the damaging effects heat and or ultraviolet light can have on lifting sling materials, in particular on nylon and polyester types of lifting slings.
Other limitations include the detrimental effects dirt, chemicals, heat, and other contaminants can have on the lifting sling core materials. In general, dirt, chemicals, and other contaminants can increase the abrasion amongst the lifting sling core fiber materials, which can result in permanent damage of the lifting sling.
Additionally there is a long felt need for a lifting sling having an indicator or electronic system attached thereto for aiding in determining when damage to the lifting sling core materials has occurred.
There is also a long felt need in the lifting sling industry for a better way to manufacture multi-core lifting slings. In this regard, quite often a multi-core lifting sling is fabricated with a series of single core members held into position by a stitched or sewn cover or sheath. As such, inspection of the multi-core lifting sling elements is difficult at best and the current preferred structure, of sewn covers or sheaths, precipitates the collection of dirt, chemicals, and contaminants which can prematurely degrade the lifting sling, hide damage, and or lead to potentially catastrophic lifting sling failure under load.
There is a need for a multi-core lifting sling that, while sealing dirt, chemicals and contaminants away from the lifting sling core materials, also binds a plurality of single core members into a superior multi-core lifting sling structure.
In addition, there is currently no way to monitor and track the use of lifting slings, including the monitoring and tracking of the types of loads that have been lifted, the frequency of use, and other telemetry and data that can be utilized to determine if the lifting sling is suitable for use and or if the lifting sling has been subjected to forces or contaminants that have damaged the lifting sling materials.
There is a long felt need for a lifting sling that can overcome these and other limitations, which in part gives rise to the following invention.